1. Field of the Invention
The invention relates in general to a conveyor mechanism wherein the conveying elements remain substantially parallel to a fixed reference plane as the conveying elements continuously travel around a closed endless loop or path, and, in particular, to a closed loop vertical lift mechanism adapted for use in an automated storage system.
2. Description of the Prior Art
Previous expedients in developing high speed storage systems having increased efficiency and flexibility in transporting containers or other objects between a conveyor system and a storage carousel system have resulted in complex and expensive systems. Typically, low cost and uncomplicated storage systems are not very efficient or flexible in their ability to handle objects of various sizes in a variety of situations. More complicated storage systems can generally be made to achieve somewhat greater efficiency and flexibility, but at much higher construction, operation and maintenance costs. Thus, there is a need for developing an uncomplicated high speed storage system at low cost having high efficiency and flexibility. Rotary storage carousels that are adapted to run continuously around a closed horizontal loop, and from which objects can be extracted and inserted on the fly are well known. Rotary storage carousels typically have many vertical arrayed tiers of object support locations on them. Objects are typically conveyed to and from the rotary storage carousel through a conveyor system. Typically, the conveyor system does not have a level for every tier on the storage carousel. An object in the input phase of the system must be moved vertically between the level of the conveyor system and the level of the location on the storage carousel where it is to be stored. It must then be inserted onto the carousel at the right location while the carousel remains in motion. Timing is obviously critical to the successful insertion of the object onto the carousel. In the extraction phase an object must be taken from its storage location on the carousel and moved to the level of the conveyor system that is to transport it away from the storage carousel. Again, timing is critical. Various previous expedients had been proposed to accomplish the timing and vertical movement of objects between the level of the conveyor and the levels of the storage locations on the rotary storage carousel. Typically, such previous expedients included a vertical lift to carry objects vertically between the level of the conveyor and the appropriate level of the rotary carousel. A transfer mechanism was typically provided to transfer objects between the vertical lift and the rotary carousel. Typically, prior proposals for transfer mechanisms included elaborate restraining and releasing mechanisms within the transfer mechanism to accomplish the necessary timing function. Alternatively, timing was accomplished by software control routines that did not require any holding of objects in the vertical lift and transfer mechanisms to accomplish the desired timing.
In general, one of the constraints in prior art rotary carousel systems had been the fact that most vertical lifts could not carry objects over the top or around the bottom of the lift. This required that objects be placed on and removed from the same reach of the lift, either the vertically up or vertically down reach. Previous devices had been proposed for vertical storage systems wherein the shelves were mounted so as to permit objects to be carried indefinitely on the system as the vertical storage system moved through cycle after cycle. See, for example, Lichti, Sr. et al., U.S. Pat. No. 5,161,929. In Lichti, Sr. et al, the shelves are pivotally suspended by four continuous guide paths and an assortment of rollers so as to remain substantially horizontal. The guide paths are separate from the loop which drive the lift. Another attempt in the art, related to storage carousels and not vertical lifts, is Soviet Union Patent No. 865,718 to Stavisskii. Here, a separate drive system moves the shelves about a horizontal loop while four individual guide paths and rollers maintain the shelves substantially parallel with a fixed reference plane. In both of these systems the drive systems are separate from the guide systems. In addition, multiple guide systems are used.
Those concerned with these problems recognize the need for a simplified vertical lift mechanism capable of holding containers continuously and indefinitely as the vertical lift traverses through cycle after cycle of the endless loop through which the mechanism travels. The timing of insertion and extraction of objects on a rotary carousel is thus greatly simplified. It is also desired that such a mechanism comprise as few parts as possible and be relatively inexpensive.
These and other difficulties of the prior art have been overcome according to the present invention.